Allow any object with respond_with_error #39

Rubyists::Leopard::MessageWrapper#respond_with_error converts its argument to a string before passing to nats-pure.

nats-pure wraps that arument with NATS::Service::ErrorWrapper, which then passes it through a case statement of Exception, Hash, ErrorWrapper, or else. else converts the error to string and sets the code to 500. If we want to build our own response to have a different code, for example 422, we would call something like Dry::Monads::Failure({ description: 'an error', code: 422 }). This gets converted to a string and the code is set to 500.

Desired behavior is for Rubyists::Leopard::MessageWrapper#respond_with_error to pass its argument without any typecasting.